Lecture 5. Enzymes in Cellular Context and in Technological and Medical Applications

Question 1

Where do a few enzymes exist and in what form?

Answer 1

A few enzymes exist as single polypeptides free in cytoplasm or extracellular medium

Question 2

What do most enzymes form?

Answer 2

Parts of larger organised structures

Question 3

How many stages are there in the oxidation of sugars in mammals?

Answer 3

3

Question 4

How are carbohydrates stored in mammals?

Answer 4

As particles of glycogen

Question 5

Where are enzymes of glycogen synthesis and breakdown located?

Answer 5

Bound to glycogen particles

Question 6

What happens in glycolysis and what is produced?

Answer 6

Glucose is converted into pyruvate which yields ATP and NADH

Question 7

Where does glycolysis take place?

Answer 7

In the cytoplasm

Question 8

Where does the citric acid/TCA cycle take place?

Answer 8

In the mitochondrial matrix

Question 9

What are the products of the TCA cycle?

Answer 9

CO₂ and NADH

Question 10

How is NADH re-oxidised?

Answer 10

By O₂ through a series of oxidation/reduction reactions (electron-transfer chain)

Question 11

What is the ribosome?

Answer 11

A complex multi-component enzyme machine for making proteins

Question 12

What is the proteasome?

Answer 12

A complex of two types of subunit to make a tightly-
controlled protein degradation machine in the cytoplasm and nucleus

Question 13

What is a frequent feature of multi-enzyme complexes?

Answer 13

The different activities are located in sequential regions of the structure

Question 14

How expensive will the enzyme market be by 2024?

Answer 14

$9.5 billion

Question 15

What contributes the most amount of money to the enzyme market?

Answer 15

Cleaning

Question 16

Traditionally, what does food bio-processing involve?

Answer 16

Intact microbes naturally present in food environment

Question 17

What is rennet?

Answer 17

A mixture of enzymes from the stomach of unweaned calves

Question 18

What is chymosin?

Answer 18

An aspartyl protease which digests casein, the major milk protein

Question 19

What does the digestion of casein do?

Answer 19

It destablizes fat droplets so milk clots, separating ‘curds’ and ‘whey’; first step in making cheese

Question 20

Process of producing chymosin on an industrial scale

Answer 20

Clone the gene encoding the enzyme and express it in bacteria or fungi
Grow the modified bacteria/fungi in biofermentors
Purify the protein

Question 21

What are proteases used for in the meat, leather and textile industries?

Answer 21

Proteases can be used to treat animal hides to remove hair and to soften skin
Proteases can be used to ‘tenderise’ meat

Question 22

What are cellulases used for in the meat, leather and textile industries?

Answer 22

Cellulases are used to treat denim to generate ‘stone-washed’ texture and look

Question 23

Since the 1970s, how have high-fructose syrups been made?

Answer 23

By including bacterial glucose isomerase

Question 24

What is used as the main sweetener in ‘diet’ drinks?

Answer 24

Aspartame/E951

Question 25

How does the hydrolysis of peptide bonds caused by proteases reversed?

Answer 25

A low-water-content solvent system (mainly organic solvent) is used to reverse the normal equilibrium

Question 26

What enzyme is not denatured in an organic solvent?

Answer 26

A thermo-stable protease named thermolysin

Question 27

Why are immobilised enzymes important?

Answer 27

They are usually more stable and more readily recoverable from reactor

Question 28

When does “beer haze” occur?

Answer 28

Often caused by barley and yeast proteins, especially at low temperatures

Question 29

How is ‘beer haze’ treated?

Answer 29

‘Chill-proof’ with proteases e.g papain

Question 30

What causes cloudiness in fruit juices?

Answer 30

Pectins from plant cell walls

Question 31

How is cloudiness removed from fruit juices?

Answer 31

Treated with pectinases

Question 32

What are enzymes better than chemistry for?

Answer 32

Stereo-specificity and positional specificity

Question 33

What are prime examples of fine chemicals that
require positional and stereo-specific synthesis?

Answer 33

Pharmaceuticals

Question 34

What is penicillin acylase used for?

Answer 34

Penicillin acylase is used to make semisynthetic penicillins

Question 35

What are biosensors?

Answer 35

Biosensors are (electronic) analytical devices giving direct read-out. Most biosensors are based on enzymes